The Seattle Familial Colorectal Cancer Registry - proposed in response to the Cooperative Family Registry for Epidemiologic Studies of Colon Cancer (CFRCC) RFA (#CA96011) -- will be a population-based resource for studies of colorectal cancer genetics. Cases will be identified by the Washington SEER program, and will include men and women aged 20-74 years with a new diagnosis of large bowel cancer. During a structured interview, first- degree family members will be identified and subsequently interviewed. For those families with a strong family history (proband plus two or more affected first-degree relatives), second- and third-degree relatives will also be interviewed. The interview will also elicit established and environmental suspected risk factors. Blood from all cases, all members of high-risk families, and a sample of other relative will be obtained, as will tumor specimens for affected subjects. For comparison, population controls will also be identified (through RDD and HCFA samples) and interviewed, and a sample will provide blood specimens. As a member of the CFRCCS, the Seattle Familial Registry will allow us to collect much needed family data, including fifth generation and environmental factors, and to address many important hypotheses through association, aggregation, segregation, and linkage analyses.